In March of last year, a motion-sensor camera caught a young golden eagle uneasily eyeing a porcupine that had wandered into its vicinity in Tuscarora State Forest near Harrisburg, Pennsylvania. A little more than a week later, the camera snapped the bird again—only this time, it had four quills sticking out from around its eyes and mouth, researchers report in a new study.
The photos provide a window into a type of wildlife interaction we rarely get to see, says Robert Murphy, a wildlife biologist at the U.S. Fish and Wildlife Service in Albuquerque, New Mexico. “It probably happens more than you think.”
For years, researchers led by Todd Katzner, a wildlife biologist with the U.S. Geological Survey in Boise, have been developing a network of camera sites that stretches from Maine to Alabama and Florida to study golden eagles in the wild. Each winter, they pile roadkill, mostly white-tailed deer, at the sites to lure the birds and other predators and scavengers to the cameras.
Katzner has studied birds of prey from Kazakhstan to Idaho, but he started his career looking at prey, researching pygmy rabbits in Wyoming for his master’s degree. The carnage, however, was too much for him. “When you study rabbits, everybody dies,” he says. ”It’s a little depressing to study prey species like that.”
Katzner has tracked golden eagles in eastern North America for nearly a decade now, but when he saw the photos of the quilled eagle, he was floored. “It was the first time I had reason to believe birds and porcupines interact,” he says. “We wanted to know if others had noticed the same thing.”
The scientists combed through several databases of scientific articles, searching for the word “porcupine” and compiling articles that mentioned avian-porcupine interactions. In 17 studies, dating from 1909 to 2009, they found reports of at least nine bird species that had known the pain of the rodent’s hostile quills, the researchers report in the current issue of The Wilson Journal of Ornithology.
Included in the list were other golden eagles, a bald eagle, a peregrine falcon, a few great horned owls, several hawks, and even a ruffed grouse. In seven cases, the spines proved fatal or nearly so. One badly injured great horned owl was put down. The grouse, which had taken eight spines in the breast, healed. In six cases, however, the researchers were left to wonder what had happened to the bird, including their own. The eagle—not quite a year old at the time—probably perished from infection, the scientists say.
The situation, however, may not always be that dire, points out Uldis Roze, a professor emeritus at Queens College at the City University of New York, who was not involved in the study but who has spent decades studying North American porcupines. Once, at the beginning of his career, he was whacked by the tail of a porcupine he had pursued up a tree in the Catskill Mountains. One of the spines disappeared completely into his upper right arm. By the time he had driven home, in agonizing pain, to New York City, he could feel the quill moving in his body. Because quills have barbs on their tips, they wiggle in as muscles contract around them.
Several days later, the quill emerged on its own from Roze’s lower arm, without any sign of infection. That experience left him wondering if quills could contain antibiotics. He published subsequent research documenting that they are, in fact, covered in a greasy coating made of free fatty acids that serve as an antibiotic, likely to protect porcupines from their own misadventures, like a misplaced foot on an unsteady tree branch.
Yet quills are quills, and many animals are content to let porcupines be. With the curious exception of the grouse, the bird species that had tangled with porcupines in these cases were predators or scavengers—and likely hungry enough to take their chances, the researchers assume.
Golden eagles, the largest eagles in North America, are versatile predators, preying upon small mammals like rabbits and wild piglets and, occasionally, larger ones like deer. In lean times, they will stoop to carrion. Although no one argues that quills are a pressing threat to the eagles, the research does serve as a reminder that sometimes predation can be as dangerous for the hunter as the hunted, the scientists say.
“It certainly had an impact on that bird,” Murphy says.